Gas Miles remaining very inaccurate

[dradams13]

I am not sure if this is the correct forum or not, hopefully I can find the right place if not.

Obviously gas mileage varies based on the type of driver you are, whether you drive in the city or on the open road, and whether or not you push the shiny sport button, but one thing I have found is that when the gas idiot light comes on at about 30 miles remaining, I can drive about 100 more miles or so before I feel like I am empty. I have a SGT, which says it has a 13.5 gallon (US) fuel tank. I get about 300 miles per tank city driving, and I am a fairly aggressive driver in the city of Chicago, and I like to open it up when I am on Lake Shore Drive or an open highway.

At first I would let it run to zero and fill up, but I was noticing that I was only putting about 11.5+/- gallons in the tank, which would mean about 2 gallons still in the tank at "0" and if you believe the average MPG displayed would mean there was at a minimum 50 miles left before empty. Then I would put the trip OD on and drive for about 50 miles and fill up and I was still about 1 gallon safe. The most I have pushed it is 70 miles after "zero". I have never and would never purposely run the car dry, so there isn't a lock solid control for distance, but it seems very inaccurate. I never really had this problem with my other Mazda3sGT, the 2011 I had. The mileage was pretty accurate from what I remember. My '14 has a smaller tank and better mileage, but I seem to have the same range. I don't get it.

Anyone have any thoughts?

 

[Google]

That's nothing new really. On the 06 GT it wasn't accurate either. For that matter, I don't recall any onboard system to be accurate. I have driven at least 50 MPG more when the system said I had 0 left, both on the previous generation Mazda3s or the new 2014.

The best way is to either get an app to do the math for you or calculate your mpg yourself over a period of a month based on full fill ups (that's the most accurate) and then you can reasonably accurate determine how much is remaining. In the winter of course, your MPG will take a huge hit so take that into account.

 

[Bruns]

Mine has always been ridiculously accurate. To the 0.0
I ways do the maths and it matches perfectly.


The major factor is whether you always use i-stop


Sent from my iPhone using Tapatalk

 

[brandini]

Run it dry and see why they do that, with two fuel pumps and direct injection you'll cry more than a gallon of tears for the death of dollars in your wallet.

Stop running it that close to empty for your own sake.

 

[Gene R]

How can you tell if you're filling the tank up? I would top off my last vehicle so I knew exactly how much gas was in the tank. I could get slightly over 3 more gallons in after the first click off. I'm not incline to to that with my 3 so I'm never quite sure how "full" it really is. I try going to the same pump all the time and letting it click 2 more times. But just seems so inaccurate. Any ideas?

 

[brandini]

Stop topping off, fill slower as you hear it filling up and you'll get more in there naturally and without risking an overfill and damage to the evap system.

So it really boils down to:
1) fill up before empty so you don't run dry and cause yourself a non-warranty dealer visit and also premature death of the fuel pump which is cooled by the fuel in the tank
2) fill up slowly to allow all of the turbulent gasoline bubbles to pop and not back up in the filler neck causing pump shutoff prematurely

I realize these both take time, but time is cheap compared to the repairs/damage these can cause.

 

[Google]

It's a good idea not to wait till your gas light comes on, but I know many people who only fill up at that point or fill up a little bit because gas is so expensive. Some have been doing this for over 9+ years with the same car and never had a fuel pump or fuel injection issue.

 

[dradams13]

Well, I am looking for range, so I don't fill up until I need to do so. I tend to do a combination of city and hwy driving so I never relied on the computer's average mpg. But when I filled up today and did the math, it was on point. I was just looking for an accurate visual aid while driving to figure out how much gas I have left. When you are going 80 on the hwy, it is not practical to wip out the phone and fumble with an app or calculator.

I dont have i-stop so that is not an issue. I didn't bother getting the tech package, it didn't seem worth the extra money.

I always fill slowly and do full fillups, and haven't topped off yet.

I was just making sure that I was not alone in my observations about the fuel mileage.

 

[gasman64]

My Mazda 3 also does the same thing. Usually have another 2.5 to 3 gallons in tank when gauge is on empty and light icon comes on. Just got it 4 weeks ago.

 

[Google]

^ there is something wrong with your module if your low fuel comes on and you have 0 fuel left or are on empty.

What's suppose to happen is the your fuel warning light goes on before you are on E and you should have an approximate number of miles or kilometers remaining. You can toggle this on your steering wheel control on the INFO button.

 

[dradams13]

^ there is something wrong with your module if your low fuel comes on and you have 0 fuel left or are on empty.

What's suppose to happen is the your fuel warning light goes on before you are on E and you should have an approximate number of miles or kilometers remaining. You can toggle this on your steering wheel control on the INFO button.

My low fuel warning light comes on when the miles remaining is at about 30 miles. However, that is not accurate. If I wait until it hits zero miles left, and fill up I only put in about 11 gallons on a 13.5 gallon tank. Like I said I can drive about 70 miles or so beyond the zero miles left, or about 300 miles per tank. I am currently sitting at 22.3 mpg on the info screen, and that checks with the math at fillups.

So yes I agree that there is something wrong, because it is coming on too early.

 

[larson701]

What you are experiencing is typical. There is normally 2-3 gallons remaining when the gauge indicates 0 gallons remaining. The amount required to fill the tank once the low fuel warning illuminates or the last bar on the fuel gauge disappears (does it?) should be consistent. Your assumption that 0 bars equals an empty tank is incorrect.